Important icons in Final Fantasy VII, that symbolize Cloud and Aerith's relationship.
Flowers Blooming in the Church is their symbol theme. When Cloud and Aerith re-meet, the theme plays. And even in areas like the Sleeping Forest dream, when Cloud has a dream of Aerith, and there they shared their last moment. Even when Cloud is in that tunnel on his way to face Sephiroth, you can hear some of that theme playing... I believe in Cloud's mind, he was thinking of Aerith.
The Lifestream is another important symbol. When Aerith is killed, Cloud places her in the Ancient lake at the Forgotten City. It's obvious that she landed in the Lifestream. Because at the end of the second disc, Cloud says something like, "now she's stuck in the Lifestream." In the early second disc, Cloud is taken hostage by Sephiroth, and also lands in the Lifestream, and gets Mako poisoning. And at the end of the game, he sees her hand. And when he tries to reach it, he can't. At this point (in my opinion) he figured out that she will now be moving on from the Lifestream, to the Promised Land.
The game has placed the 'Promised Land' in an area in the Northern Crater. I believe the Promised Land is indeed, the afterlife. Which promises endless happiness. You can only live in a world of boundless happiness if it was the afterlife. The Shinra believe that it is full of Mako energy. Mako energy will only kill the Planet because Mako reactors suck up Spirital Energy and that gets used up and thrown away. So I doubt Mako is in the Promised Land. At the end of the game, Cloud makes a statement, "I think I'm beginning to understand. An answer from the Planet, the Promised Land. I think I can meet her...there." Evidently, Cloud believes the Promised Land is where he can meet and be with Aerith.
Cloud tries for Aerith's hand, there is a bright light surrounding her hand. Aerith was known as the "bright spot" in Midgar. She also brightened up Cloud when they got to know eachother. Even in Kingdom Hearts, Cloud says he is searching for his "light." In which, I believe he means Aerith.